Under the Crown of Scattered Beech (Fagus sylvatica): Impact on Plant Community, Soil Resources, and Fungal Diversity

Question: Scattered trees are easily discernible in landscapes worldwide. They are integral to "wooded grassland" ecosystems, characterized by grazed and/or mowed open areas. In the Mediterranean basin, these dynamic systems are threatened by the abandonment of traditional management of marginal areas. Despite the ecological relevance of wooded grasslands and the importance of scattered trees for biodiversity, few holistic studies consider multiple ecosystem components simultaneously, and none focus on the Apennine area. This study aims to investigate the ecological impact of large scattered Fagus sylvatica trees on seminatural grasslands. Location: Central Apennines, Italy. Methods: Following a distance gradient from the tree trunk towards the open grassland, we established four distinct sampling positions. At each position, we conducted an analysis encompassing a range of ecosystem components. This included vegetation composition and productivity, soil chemistry, root density, hydrological properties, light availability, and soil fungal diversity. Results: Plant species richness, aboveground live biomass, and ground light availability exhibited a positive correlation with increasing distance from the trunk, signifying a gradual transition towards a more diverse and open grassland community. Conversely, litter and root biomass exhibited a negative correlation, decreasing with distance from the beech trees. Soil pH and nitrogen content increased with distance from the trunk, suggesting spatial heterogeneity in nutrient availability driven by the influence of the beech. Finally, four distinct plant communities were recorded with different abundances of all fungal taxa communities related to the plot from the trunk towards grassland. By examining the soil fungal abundance and diversity, we highlighted differences among soil plots correlated with different fungal functional guilds, highlighting a clear zonation effect mediated by the scattered beech trees. Conclusions: At a landscape scale, the coexistence of isolated trees and grasslands increases biodiversity, while the abandonment of traditional practices with forest recolonization leads to homogenization. Regional and local policies should identify management practices to protect this valuable ecosystem.